Fiber – Part I: The Inadequate Intake of Dietary Fiber inthe United States: Trends and Recommendations

Michael Garko, Ph.D.

Producer and Host of Let’s Talk Nutrition

Introduction

It lacks nutrients. It is indigestible. It is calorie/energy resistant. Yet, paradoxically, fiber is one of the most important food substances to consume to help create, sustain and reclaim health, wellness and well-being.

Due to the media’s more focused attention on and reporting of health and nutrition issues related to dietary fiber, education programs and campaigns on dietary fiber promoted by governmental and private health agencies and the commercializing, marketing and selling of dietary fiber (along with Grandma’s advice to eat more fiber), a large segment of the population knows it needs to consume an adequate amount of daily fiber, if for no other reason than to avoid becoming constipated.

There has been a concerted effort on the part of private and governmental agencies and healthcare professionals to educate health consumers on how dietary fiber can contribute to better overall health and prevent the serious detrimental health consequences stemming from a less than optimal daily intake of dietary fiber. However, as it will be learned, despite all of its well-established and well-publicized health benefits, Americans still consume a woefully inadequate amount of dietary fiber

The June, 2013, issue of Health and Wellness Monthly is the first in a series of articles on dietary fiber. This month’s issue will focus on trends associated with dietary fiber intake in the United States, trends which reflect an inadequate intake of dietary fiber. Attention will also be given to recommendations on how much fiber should be consumed so as to prevent disease and promote health.

Inadequate Intake of Dietary Fiber

It is an understatement to assert that Americans do not consume a sufficient amount of dietary fiber. In fact, there is a real and measurable dietary fiber deficiency, which exists in the United States and which is among the more important factors contributing to the ill health of tens of millions of Americans, an issue to be examined later in this series on dietary fiber.

Dietary Fiber Intakes From 1988-1991

In 1994, based on data from the Third National Health and Nutrition Examination Survey, Phase 1, 1988-1991, Alaimo et al. (1994) reported that the average/mean daily intake of dietary fiber was 14.82 grams, while the average/median intake of dietary fiber was lower at 12.63 grams. In terms of gender, the average/mean daily intake of dietary fiber was 17.01 grams and 12.75 grams for males and females, respectively. The average/median dietary fiber intake was 14.73 and 11.24 grams a day for males and females, respectively.

With adults younger than 70 years of age, daily dietary fiber intakes were the highest among Mexican Americans, followed by non-Hispanic whites and non-Hispanic blacks. As would be expected, the average/mean daily dietary fiber intakes were generally higher among adults compared to children and adolescents (see Alaimo et al., 1994) but still far below what was recommended.

At the time of Alaimo et al.’s study in 1994, the National Cancer Institute (NCI) (1987) recommended that adults consume 20-30 grams of dietary fiber daily. Alaimo et al. (1994) reported that the only groups in their study whose average/mean intakes reached the NCI’s goals were Mexican American males 16-69 years of age with a range of 20-26 grams a day and non-Hispanic white males 30-39 years of age at 20 grams a day.

Dietary Fiber Intakes From 1999-2008

Based on the National Health and Nutrition Examination Survey looking at dietary fiber intake trends in the United States from 1999-2008, King et al., (2012) reported that the average daily intake of dietary fiber for 1999-2000 was 15.6 grams a day, for 2001-2002 it was 16.1 grams a day, for 2003-2004 it was 15.5 grams a day, for 2005-2006 it was 15.8 grams a day and for 2007-2008 the average daily intake was 15.9 grams day. Hence, taking the findings from both studies, the average daily intake of dietary fiber from 1988-2006 ranged from 15.5 grams to 16.1 grams a day.

King et al., (2012) reported that study participants who were obese (body mass index ≥30) had a lower dietary fiber intake compared to those with normal weight or overweight (14.6 to 15.4 g/day and 15.6 to 16.8 g/day, respectively.

In terms of race-ethnicity, Mexican Americans consumed significantly higher intake in 1999-2000 compared to non-Hispanic whites (i.e., 18.0 vs. 16.1grams a day), while the intake of Mexican Americans failed to increase over time (i.e., 17.7 grams a day in 2007-2008). The dietary fiber intake of Non-Hispanic blacks was 12.5 grams a day at baseline and increased slightly to 13.1 grams a day by 2007-2008 (see King et al., 2012).

Recommendations For Adequate Intake of Dietary Fiber

There are far too many health organizations and agencies offering dietary fiber intakerecommendations to be considered here. However, the health agencies presented are illustrative of recognized health organizations (e.g., American Heart Association, American Cancer Society, World Health Organization, etc.) offering dietary fiber intake recommendations.

U.S. Dept. of Agriculture and U.S. Dept. of Health and Human Services

In its Dietary Guidelines for Americans 2010, the U.S. Department of Agriculture and U.S. Department of Health and Human Services (2010, December) recommends an adequate intake of dietary fiber should be at 14 grams per 1,000 calories, or stated another way 25 grams per day for women and 38 grams per day for men, with most Americans under consuming dietary fiber at only 15 grams a day on average.

Centers for Disease Control and Prevention

Following the Dietary Guidelines for Americans 2010 (U.S. Department of Agriculture and U.S. Department of Health and Human Services (2010, December), the Centers for Disease Control and Prevention (CDC) (2012) recommends consuming 14 grams of fiber per 1,000 calories or 25 grams of fiber per day for women to 38 grams for men. Using the Institute of Medicine guidelines, the CDC offered the following intakes for dietary fiber based on age and gender:

nutrient
(units)

source
of goals

child
1–3

female
4–8

Male
4–8

female
9–13

Male
9–13

female
14–18

Male
14–18

female
19–30

Male
19–30

female
31–50

Male
31–50

female
51+

Male
51+

Total fiber (grams)

IOMd

14

17

20

22

25

25

31

28

34

25

31

22

28

Source: Centers for Disease Control and Prevention (2012)

National Cancer Institute

When discussing dietary fiber especially within the context of nutrition in cancer care and treatment of symptoms (e.g., constipation), the National Cancer Institute (NCI) (2011) recommends 25-35 grams of dietary fiber daily, gradually increasing the amount of fiber each day and drinking plenty of fluids to help move the fiber through the intestines.

Institute of Medicine

Below are the Institute of Medicine (IOM) (2005) recommendations for the adequate intake (AI) of total fiber.[1]

Total Fiber Adequate Intake Summary, Ages 1-18

Adequate Intake for Children

1–3 years 19 g/d of Total Fiber

4–8 years 25 g/d of Total Fiber

AI for Boys

9–13 years 31 g/d of Total Fiber

14–18 years 38 g/d of Total Fiber

AI for Girls

9–13 years 26 g/d of Total Fiber

14–18 years 26 g/d of Total Fiber

Total Fiber Adequate Intake Summary, Ages 19 and Older

AI for Men

19–30 years 38 g/d of Total Fiber

31–50 years 38 g/d of Total Fiber

51–70 years 30 g/d of Total Fiber

> 70 years 30 g/d of Total Fiber

AI for Women

19–30 years 25 g/d of Total Fiber

31–50 years 25 g/d of Total Fiber

51–70 years 21 g/d of Total Fiber

> 70 years 21 g/d of Total Fiber

Source: Institute of Medicine (2005)

Conclusion

There is little doubt that the intake of dietary fiber is less than adequate. Over the 20 year period of the two studies presented, the average/mean daily intake of dietary fiber ranged from 14.82 to 16.1 grams a day. These daily average intakes of dietary fiber are considerably far from any of the recommended daily intakes of the U.S. Department of Agriculture and U.S. Department of Health and Human Services (2010, December), Centers for Disease Control and Prevention (2013), National Cancer Institute (2011) or Institute of Medicine (2005).

The recommendations ranged from 19 grams a day (children 1-3 years of age) to 38 grams (men 19-50 years of age). Using a different metric, another recommendation was 14 grams per 1,000 calories. Averaging the means of the range intake averages (i.e., 14.82 & 16.1 grams), Americans consume approximately 15 grams a day. Men tend to consume more fiber than women, race-ethnicity notwithstanding. Mexican-Americans consume more dietary fiber than other ethnic groups. The elderly tend to consume less fiber than those not as deep into the lifespan. Adults consume more dietary fiber than children and adolescents.

From 1988 to 2008, there was virtually no improvement in the consumption of dietary fiber. This is not surprising. The production and consumption of processed foods high in salt, sugar and fat and low in fiber has increased significantly over the past 20 years and shows no signs of abating. It is clear that the strategy of health professionals just telling people to eat more fruits, vegetables, legumes and other fiber-rich foods is not working. In upcoming articles in the series on dietary fiber, the issue of persuading people to consume more dietary fiber will be featured, along with specific strategies and tactics to include more fiber in peoples’ day-to-day diet. Next month’s issue of Health and Wellness Monthly will address the complexity and controversy surrounding the search for a scientific, universally accepted definition of dietary fiber.

[1] The IOM (2005) defines total fiber as the “sum of Dietary Fiber and Functional Fiber (p. 339). It defines dietary fiber as consisting of “nondigestible carbohydrates and lignin that are intrinsic and intact in plants (Institute of Medicine, 2005, p. 339) and functional fiber as consisting of “isolated, nondigestible carbohydrates that have beneficial physiological effects in humans (Institute of Medicine, 2005, p. 339).